A 26-year-old man will be charged with the murder of British backpacker Grace Millane.
He spoke with police all Saturday afternoon, after he was found at a central Auckland address.
Ms Millane, 22, was last seen with the suspect late last Saturday evening (December 1) at the CityLife Hotel. It is unknown if she left there alive.
He will be held in police custody until Monday morning, when he will appear in Auckland District Court.
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Det Insp Scott Beard said on Saturday their thoughts are with the 22-year-old's family.
"Sadly the evidence we have gathered to this point in this inquiry has established that this is a homicide," he told reporters.
"We still do not know where Grace is. We are determined to find her and return her to her family."
A vehicle of interest has also been taken in for forensic examination.
"We are now making inquiries to find out exactly where that vehicle has been," said Insp Beard.
Police will try to track its movements using GPS and cellphone tower data.
Earlier on Saturday police released images of some of Ms Millane's belongings, which were also missing. Police believe the alleged killer might have tried to get rid of them.
There has been speculation the pair met using a dating app, but police wouldn't comment.